1. Field of the Invention
The present invention relates to a technology of spatial filtering that selects target terminals only located within a predetermined distance among a plurality of targets using a difference in propagation delay between an electromagnetic signal and an acoustic signal.
2. Description of the Related Art
In conventional arts, one of general problems that occurs in wireless communications is the problem of selecting a peer to communicate with among a plurality of neighboring terminals. In particular, the problem frequently occurs in localized wireless communications such as device-to-device (D2D) communications recently drawing much interest.
Methods widely used to select a target terminal for communication include a scan and select method used in various communications protocols such as Bluetooth. According to the scan and select method, a terminal scans neighboring terminals and a user selects a target terminal to communicate with from a list of neighboring terminals found by the scan. However, the scan and select method takes a long time for scanning and, moreover, may give an extremely long list of the neighboring terminals to the user when numerous neighboring terminals are found by the scan.
In this case, spatial filtering may be used, which filters neighboring terminals using location information of the target terminal to communicate with. Therefore, time required for selecting a target terminal may be greatly reduced. In addition, user convenience may be greatly improved.